1. Field of the Invention
The present invention relates to a structure of connecting a coaxial cable to an electric circuit substrate and a structure of connecting a coaxial cable to an electric circuit substrate preferably applied to an electric device testing apparatus for testing a semiconductor integrated circuit element and other variety of electric devices (hereinafter, also simply referred to as an IC).
2. Description of the Related Art
An electronic devices testing apparatus called a xe2x80x9chandlerxe2x80x9d conveys a large number of ICs held on a tray to inside of a testing apparatus where the ICs are pressed against socket terminals connected to a test head, then the IC testing unit (tester) is made to perform a test. When the test is ended, the ICs are conveyed out from the test procedure and reloaded on trays in accordance with results of the tests so as to classify them into categories of good ICs and defective ones.
Here, a socket board 505 (an electric circuit substrate) of the test heads is connected to a coaxial cable 506 shown in FIG. 5. In the related art, a coaxial cable was connected to a socket board by soldering a core wire 506a of the coaxial cable 506 to the socket board 505 and a jumper cable J soldered to the socket board 505 and a shield 506b of the coaxial cable 506 were twisted together and soldered. By connecting a large number of such coaxial cables 506 to the socket board 505, sending and receiving of test signals is performed between the tester and the test head at the time of pressing ICs against socket terminals.
In the above connection structure of a coaxial cable to a socket board in the related art, however, since the core wire 506a constituting a signal line and the jumper cable J constituting an earth line were connected one to one, a space S between the core wire 506a and the jumper cable J needs to be at least 2 to 3 mm, so there was a disadvantage that a packaging density of the coaxial cable 506 could not be made higher.
Also, since an earth line was configured by connecting the jumper cable J and the shield 506b, the earth line inevitably became long, consequently, there was a disadvantage that inductance of a high frequency range increased and frequency characteristics declined.
Furthermore, there was a disadvantage that consistency of impedance of a signal was poor since exposing portions of an insulation body 506c of the core wire was large and not covered by the shield 506b. 
An object of the present invention is to provide a connection structure of a coaxial cable to an electric circuit substrate which can heighten a packaging density of coaxial cables and has excellent electric characteristics.
According to the present invention, there is provided a connection structure of a coaxial cable to an electric circuit substrate, comprising a cable block connected to a ground line of the electric circuit substrate and a coaxial cable wherein the ground line is connected to said cable block.
In this connection structure, since a ground line of a coaxial cable is connected to a ground line of an electric circuit substrate via a cable block connected to the ground line of the electric circuit substrate, a plurality of coaxial cables can be grounded by one cable block. Accordingly, an area occupied by the ground line of the electric circuit substrate becomes smaller and a higher packaging density of coaxial cables becomes attainable. Also, since the ground line of the coaxial cable is directly connected to the cable block, the length of the ground line becomes shorter and frequency characteristics improves. Furthermore, by directly connecting the ground line of the coaxial cable to the cable block, the core wire is covered by the ground line to the end of the coaxial cable, as a result, consistency of impedance of signals becomes preferable.
It is not particularly limited in the above invention, but the cable block preferably has a concave portion in accordance with an outward form of the coaxial cable, and the ground line of the coaxial cable is connected to the concave portion.
By setting an outward form of the coaxial cable in a concave portion of the cable block at the time of connecting the ground line of the coaxial cable to the cable block, a position of the core wire of the coaxial cable can be made accurate.
Also, it is not particularly limited in the above invention, but the core wire of the above coaxial cable is preferably connected to a land of a signal line of the above electric circuit substrate.
By connecting the core wire of the coaxial cable to the land of the signal line, connection bias becomes small and a capacity can be made small.
Particularly, as explained above, since the position of the core wire of the coaxial cable is accurately determined by setting the ground line of the coaxial cable in the concave portion in the cable block, relative position with respect to the land of the signal line can be also made accurate.
Also, it is not particularly limited in the above invention, but preferably, the above cable block is formed a conductive material layer, for example, a copper plating layer on a surface of the substrate.
By making a plating layer by a conductive material having a large heat capacity, a temperature rising speed at the time of soldering.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.